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<DIV><FONT size=2>As far as I have seen when adjusting valves any valve is at
peak lift at only one point on the cam. The tip of the lobe is rounded, so
as it passes under the flat tappet it is only when the centre of the lobe is
under the centre of the follower that you will have peak lift. Very nearly
peak lift a few degrees either side of that, but not much.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>You mention comparing valves 1 and 8, but talk about inlet and
exhaust. It's true that inlet and exhaust lobes are not 180 degrees apart
- the lobe of an inlet is 16 degrees away from the heel of an exhaust and
vice-versa, but 1 and 8 are both exhaust valves. And because those
valves are on cylinders 1 and 4 which fire one complete engine revolution
apart it wouldn't surprise me if their lobes and heels *are* 180 degrees
apart, which is probably why someone came up with the Rule of Nine. All
the pairs in the Rule of Nine are the same valve - inlet or exhaust - and all
on 'opposite' halves of the engine.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>But all this is getting into the realm of how many angels can
dance on the head of a pin. The fact remains that in theory there is a
significant range of cam rotation where the clearance should be at a
maximum, meaning that it shouldn't be critical to get the opposite valve exactly
on the peak of its lobe. But in practice, on a cam by cam basis, that
doesn't seem to be the case and one needs to check where the point of maximum
gap is on any valve, and see how that compares with the point of maximum lift on
its partner valve. As I've said a couple of times on engines I've checked
the two don't always occur at the same time on various valves. It's also
the case that the period of maximum gap has been surprisingly narrow, like the
period of maximum lift, whereas on drawings of various cam profiles the base
circle i.e. where the clearance should be maximum occupies more than 180
degrees.</FONT></DIV>
<DIV><FONT size=2></FONT> </DIV>
<DIV><FONT size=2>PaulH.</FONT></DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV style="FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: black"><SPAN
style="COLOR: #1f497d">... does the TL of valve 8 mean that you have
found the BL of valve 1? If I remember correctly, they aren’t 180 opposite,
input being before or after exhaust by some degrees. Is the difference of
opposition so insignificant that it doesn’t
matter?</SPAN></DIV></BLOCKQUOTE></BODY></HTML>